In the case where the joint strength of the joint part of a joinable member is strictly required to have joint strength, a bolted joint having a plurality of bolts arranged in a load direction is used as a coupling means. As a result, the load applied to the joint part is shared by the bolted joint.
In Patent literature 1, it is disclosed to use these bolted joints for joining blade panels or the like of an aircraft.
A conventional bolted joint structure using a plurality of bolts is illustrated in FIG. 7. The bolt join structure 100 is configured such that a plurality of joint bolts 104a-104d (four bolts in FIG. 7) for two plates 102a, 102 to be joined are arranged along a direction of tensile load F.
In the bolted joint structure 100, generally bolts 104b, 104c disposed on a center side have less shared load than bolts 104a, 104d disposed on an outer end side due to small deflection difference of the plates which each transmit the load on the joint parts to the bolts. This state is indicated by line A in FIG. 3.
In the case where the joint parts of the joinable member is made of a composite material, the shared load between the bolts on the outer end side tend to be larger as the composite material has lower ductility than metal. Therefore, it is difficult to increase the load on the joint parts even by using more bolts to join the joint parts.